Bleach Stabilizer Compositions And Methods

ABSTRACT

Compositions for and methods of stabilizing bleaching and making paper or paperboard having suitable brightness are provided. A stabilizer composition is provided containing aminocarboxylate, hydroxy acid, and either polyamino acid or iminodisuccinate, or both. The stabilizer composition can have low levels or be free of magnesium, phosphates, and silicates. The present invention also relates to a method of stabilizing the bleaching of pulp at an alkaline pH.

This application claims the benefit under 35 U.S.C. §119(e) of prior U.S. Provisional Patent Application No. 61/755,496, filed Jan. 23, 2013, which is incorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to the stabilization of paper pulp bleaching. More particularly, this invention relates to compositions containing stabilizing agents and methods of using such compositions in the bleaching of paper pulp to yield superior paper products.

Papermaking generally includes forming an aqueous pulp composition and then sheeting and drying the pulp to form a desired paper product. Hydrogen peroxide is widely used in industrial and domestic applications. Hydrogen peroxide is extensively used, for example, in the production of pulp, such as in the production of recycled pulp, to enhance pulp and paper brightness by bleaching. Various agents such as magnesium salts, phosphates, and sulfates have been used to stabilize hydrogen peroxide. Unfortunately, the use of such agents also has serious negative effects on both the paper making process itself and on the environment. Silicates and magnesium salts contribute to scale deposition on paper making machinery. Phosphates can act as fertilizers and contribute to an increase in damaging algal blooms. However, phosphates are very good stabilizing agents and their removal results in poor bleaching with no obvious replacement. Satisfactory chelants can be hard to identify and some, for example, nitrilotriacetic acid (NTA) have been listed as carcinogens. Accordingly, there exists a need for compositions and methods for stabilizing hydrogen peroxide, as well as other bleaching agents, that avoid the use of agents such as magnesium salts, phosphates, and silicates, as well as problematic chelants.

SUMMARY OF THE INVENTION

A feature of the present invention is to provide compositions and methods for stabilizing the bleaching of paper pulp.

A further feature is to provide compositions and methods for stabilizing the bleaching of paper pulp essentially free of magnesium, phosphate, and/or silicate.

Another feature of the present invention is to provide compositions and methods for treating paper pulp to obtain paper products having superior brightness.

Still another feature of the present invention is to provide compositions and methods for sequestering metal ions and/or achieving low manganese to iron ratios in treated pulp and resulting paper products.

Yet another feature of the present invention is to provide chelants, alkaline cleaning-in-place (CIP) agents, scale inhibitors, felt cleaners, viscosity reduction agents, corrosion inhibitors, and anti-freeze agents.

Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and obtained by means of the elements and combinations particularly pointed out in the written description and appended claims.

To achieve these and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a stabilizer composition including: a) about 50 wt % to about 80 wt % of at least one aminocarboxylate; b) about 5.0 wt % to about 20 wt % of at least one hydroxy acid; and c) about 1.0 wt % to about 10 wt % of at least one polyamino acid, at least one iminodisuccinate, or both, wherein a), b), and c) are different from each other, and wherein each wt % is based on the total weight of the stabilizer composition. The stabilizer composition can have low levels or be essentially free of magnesium, phosphates, and silicates. The present invention also relates to a method of stabilizing the bleaching of pulp at an alkaline pH. The method can include adding from about 1.0 lb. to about 5.0 lbs. per dry ton of pulp of a stabilizer composition of the present invention to a pulp composition prior to any bleaching of said pulp composition; and adding at least one peroxide to the pulp composition at an alkaline pH after addition of the stabilizer composition to form a bleached pulp.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are only intended to provide a further explanation of the present invention, as claimed.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention provides a stabilizer composition that contains, comprises, consists essentially of, or consists of: a) about 50 wt % to about 80 wt % of at least one aminocarboxylate; b) about 5.0 wt % to about 20 wt % of at least one hydroxy acid; and c) about 1.0 wt % to about 10 wt % of at least one polyamino acid, at least one iminodisuccinate, or both, wherein a), b), and c) are different from each other, and wherein each wt % is based on the total weight of the stabilizer composition. The stabilizer composition can include water and/or other aqueous components and/or other ingredients. Water can be added at any stage in any amount to arrive at a desired concentration. The stabilizer composition can chelate metals in the pulp composition/slurry/solution and thus can provide a much improved environment for subsequent bleaching. In this way, the metals are trapped or substantially trapped and/or otherwise do not interfere with bleaching or bleaching agents or bleaching conditions.

The amount of magnesium present in the stabilizer composition can be minimized or eliminated. For example, the stabilizer composition can contain less than 1.0 wt %, less than 0.5 wt %, less than 0.05 wt %, less than 0.001 wt %, less than 0.0001 wt %, or less than 0.00005 wt %, or 0 wt % magnesium based on the total weight of the stabilizer composition. The magnesium can be or include any one or a combination of elemental magnesium, one or more magnesium salts, one or more magnesium ions, one or more magnesium radicals, and/or any other form of magnesium. The methods of the present invention can exclude or minimize the addition of any form of magnesium during or prior to the bleaching of paper pulp. The methods can exclude or minimize addition of magnesium at later stages.

The amount of phosphate in the stabilizer composition can be minimized. For example, the stabilizer composition can contain less than 1.0 wt %, less than 0.5 wt %, less than 0.05 wt %, less than 0.001 wt %, less than 0.0001 wt %, or less than 0.00005 wt % or 0 wt % phosphate based on the total weight of the stabilizer composition. The phosphate can be or include any one or a combination of monophosphate, polyphosphate, one or more phosphate salts, one or more phosphate ions, one or more phosphate radicals, and/or any other form of phosphate. The methods of the present invention can exclude the addition of any form of phosphate during or prior to the bleaching of paper pulp. The methods can exclude or minimize addition of phosphate at later stages.

The amount of silicate in the stabilizer composition can be minimized. For example, the stabilizer composition can contain less than 1.0 wt %, less than 0.5 wt %, less than 0.05 wt %, less than 0.001 wt %, less than 0.0001 wt %, or less than 0.00005 wt % or 0 wt % silicate based on the total weight of the stabilizer composition. The silicate can be or include any one or combination of monosilicate, polysilicate, one or more silicate salts, one or more silicate ions, one or more silicate radicals, and/or any other form of silicate. The methods can exclude the addition of any form of silicate during or prior to the bleaching of paper pulp. The methods can exclude or minimize addition of silicate at later stages.

The at least one aminocarboxylate of the stabilizer composition can be present in an amount from less than 20 wt %, from about 20 wt % to about 95 wt %, from about 35 wt % to about 85 wt %, from about 50 wt % to about 80 wt %, from about 55 wt % to about 75 wt %, from about 60 wt % to about 70 wt %, greater than 95 wt %, or any other intervening amount based on the total weight of the stabilizer composition. Any appropriate aminocarboxylate or combination of aminocarboxylates can be used. For example, the at least one aminocarboxylate can be or include one or more of ethylenediaminetetraacetate (EDTA), diethylene triamine pentaacetate (DTPA) (available, for instance, as Dissolvine® from AkzoNobel, Amsterdam, Netherlands and as Versenex™ from Dow Chemical, Midland, Mich.), glycine, nitrilotriacetate (NTA), ethylene glycol tetraacetate (EGTA), 1,4,7,10-tetraazacyclo dodecane-1,4,7,10-tetraacetate (DOTA), 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetate (BAPTA), N,N′-ethylenediamine disuccinic acid (EDDS), glycine diacetate (GDA), methylglycine diacetate (MGDA), and/or iminodisuccinate (available as Baypure® CX 100 from Lanxess AG, Leverkusen, Germany). Aminocarboxylates are understood to include polyaminocarboxylates. The aminocarboxlate can be in the form of an acid, a conjugate base of the acid, or a salt containing one or more kind of counter ion.

The hydroxy acid of the stabilizer composition can be present in an amount less than 1.0 wt %, from about 1.0 wt % to about 50 wt %, from about 5.0 wt % to about 20 wt %, from about 7.5 wt % to about 15 wt %, from about 10 wt % to about 12.5 wt %, greater than 20 wt %, or any other intervening amount based on the total weight of the stabilizer composition. Any appropriate hydroxy acid or combination of hydroxy acids can be used. The hydroxy acid can be an alpha hydroxy acid(s). The hydroxy acid can be or include at least one of citric acid, gluconic acid, glycolic acid, lactic acid, malic acid, tartaric acid, mandelic acid, muratic acid, succinic acid, butanetetracarboxylic acid (BTCA), polyacrylic acid, poly-α-hydroxyacrylic acid (PHAS), or any combination thereof. Hydroxy acids are understood to include polyhydroxy acids. The hydroxy acid can be in the form of an acid, a conjugate base of the acid, or a salt containing one or more kind of counter ion.

The polyamino acid, iminodisuccinate, or both of the stabilizer composition can be present in an amount less than 0.1 wt %, from about 0.1 wt % to about 40 wt %, from about 0.5 wt % to about 20 wt %, from about 1.0 wt % to about 10 wt %, from about 2.5 wt % to about 7.5 wt %, greater than 40%, or any other intervening amount based on the total weight of the stabilizer composition. Any appropriate polyamino acid or combination of one or more polyamino acids and/or iminodisuccinates can be used. For example, the polyamino acid can be or include polyaspartic acid (available as A-5D or C-5D from Nanochem Solutions, Inc., Summit Argo, Ill.), and/or polyglutamic acid, or any combination thereof. Polyamino acids include polymers and copolymers of any amino acid, naturally occurring or artificially constructed, or any combination thereof. Polymers can include D-amino acids, L-amino acids, or any combination thereof. Polymers can include one or more of alpha, beta, gamma, delta, epsilon, and/or the like amino acids. Any desirable weight ratio of one type of amino acid to another can be present in a polymer. For example, the weight ratio of beta to alpha amino acids in a polyamino acid can be greater than 1, equal to 1, or less than 1. The polyamino acid, iminodisuccinate, or both can be in the form of an acid, a conjugate base of the acid, or a salt containing one or more kind of counter ion.

One example of a stabilizer composition contains DTPA, GDA, an organic acid, polyaspartic acid, and water. Another example of a stabilizer composition contains DTPA, GDA, a polyamine salt, an organic acid, polyaspartic acid, and water. Yet another example of a stabilizer composition contains DTPA, an organic acid, polyaspartic acid, and water. Still another example of a stabilizer composition contains DTPA, an organic acid, iminodisuccinate, and water. The molecular weight of the polyaspartic acid can be varied.

The stabilizing agents of the stabilizer compositions of the present invention can act synergistically to achieve a brighter pulp and/or brighter paper product than if a single or comparatively fewer stabilizing agents were used. Brightness can be judged using any accepted brightness test or any other brightness test described herein. For example, a high molecular weight polyamino acid having a beta:alpha ratio greater than one blended with a (poly)aminocarboxylate and can form a stabilizer composition capable of providing synergistically greater brightness than if either stabilizing agent were used alone. In another synergistic example, a stabilizer composition is formed from at least two different aminocarboxylates. The stabilizer can comprise at least one aminocarboxylate, at least one polyamino acid, and at least one hydroxy acid. Synergism can also be evaluated based on metal concentration and sequestration. One of the many aspects of the present invention is the appreciation that a single stabilizing agent, for example, PHAS, does not achieve satisfactory peroxide stabilization by itself. The applicants have discovered that particular combinations of stabilizing agents can achieve peroxide stabilization beyond expectation and without the use of chemicals that can have a deleterious effect on efficiency, worksite quality, and the environment generally.

Unlike the present invention, it was discovered that when an aminocarboxylate (like DTPA) was used alone or when an iminodisuccinate compound (IDS) was used alone or when a polyamino acid (e.g., a polyasparate) was used alone to determine their ability as a bleach stabilizer composition, with no phosphates present, each one by itself was essentially no better than the “control” which had no active ingredients. In other words, each one by itself was not useful at all as a bleach stabilizer. However, it was further discovered that when an aminocarboxylate (like DTPA) was used in combination with an iminodisuccinate compound or a polyamino acid, with no phosphates present, these combinations performed much better than the “control” and in fact preformed as well as bleach stabilizer compositions containing phosphates. These results were even further enhanced when a hydroxy acid was additional present in the formulations of the present invention.

The present invention provides a method of stabilizing the bleaching of pulp at an alkaline pH or acidic pH. The method can include adding from about 1.0 lb. to about 5.0 lbs. (or more) per dry ton of pulp of a stabilizer composition of the present invention to a pulp composition prior to any bleaching of the pulp composition; and then adding at least one peroxide to the pulp composition at an alkaline pH (or acidic pH) after addition of the stabilizer composition to form a bleached pulp. The present invention is particularly useful at alkaline pHs for the pulp slurry or pulp water or pulp composition. As the bleaching generally occurs at an alkaline pH, the pH of the pulp can be greater than 7.0, and can be adjusted to any desired alkaline pH. The pH of the pulp composition or water containing the pulp (prior to, during, and/or after the introduction of the stabilizer composition) can be a pH of from about 7.0 to about 14, from about 8.0 to about 14, from about 9.0 to about 12, from about 9.5 to about 11, or about 10.

The method can include heating the pulp composition to a desired temperature and/or maintaining a desired temperature. For example, the temperature can be less than 90° F., from about 90° F. to about 190° F., from about 100° F. to about 180° F., from about 110° F. to about 170° F., from about 120° F. to about 160° F., from about 125° F. to about 150° F., from about 130° F. to about 140° F., or greater than 190° F. The stabilizer composition can be optionally heated before addition to the pulp composition.

The method can include adding at least one sulfur-containing compound to the pulp composition. The sulfur-containing compound can be added at any appropriate time point, for example, prior to the addition of the at least one peroxide used for bleaching of the pulp composition, and/or after addition of the stabilizer composition. The at least one sulfur-containing compound can include, for example, a sulfite. Any suitable sulfite, salt thereof, or combination thereof can be used. Sulfites include, for example, potassium hydrogen sulfite, potassium bisulfite, potassium metabisulfite, sodium hydrogen sulfite, sodium bisulfite, sodium metabisulfite, sodium sulfite, calcium sulfite, or a combination thereof. The sulfur-containing composition can be included as part of the stabilizer composition or can be separate.

The method of the present invention can further include forming the bleached pulp into a paper product having a brightness greater that that achieved by using a single stabilizing agent. Brightness of the pulp and/or resulting paper product can be tested. Brightness can be judged using any accepted brightness test or any other brightness test described herein. For example, TAPPI Test Method T 452 om-08 can be used to measure brightness. This procedure uses a test instrument employing 45° illumination and 0° viewing geometry with the illuminating and viewing beams adjusted so that translucent materials are evaluated on an arbitrary but specific scale to measure the directional reflectance factor at 457 nm.

Each component of the stabilizing composition, and optional sulfur-containing compound, can be applied to a papermaking pulp at the same time, for example, in the form of a pre-made or pre-formed stabilizer composition, or the components can be added (in any order) sequentially within a period of time (e.g., within 1.0 second to 10 minutes) to permit the components to interact in combination with the pulp. The individual components of the stabilizing composition, and optional sulfur-containing compound, can be pre-combined as a pre-mixture, and then added together in a common composition to the pulp. The individual components, and optional sulfur-containing compound, can be co-mixed in an addition pipeline or other feedline that feeds the resulting co-mixture to an introduction port, such as a port on a pulp processing unit. The individual components, and optional sulfur-containing compound, can be added separately and simultaneously to the pulp from different introduction ports on the same processing unit. The individual stabilizing agents, and optional sulfur-containing compound, can be introduced sequentially, that is, separately at separate times, from the same or different introduction ports or locations on the papermaking system within a short period of time. In sequential addition, the individual components, and optional sulfur-containing compound, can be separately added in time with all components brought into contact in the pulp within a short period of time, for example, within about 5 minutes of each other, or within about 4 minutes of each other, or within about 2 minutes of each other, or within about 1 minute of each other, or within about 30 seconds of each other, or within shorter periods of time. The addition of the individual components, and optional sulfur-containing compound, can be similarly separated from the addition of the bleaching agent, for example, hydrogen peroxide. The resulting pulp can be further processed and formed into a paper or paperboard. Preferably, the stabilizer composition is pre-formed and then added to the pulp or pulp slurry.

Prior to adding any bleaching agent to bleach the pulp, the stabilizer composition should have sufficient time to stabilize the pulp or pulp slurry or water containing the pulp. In addition, the stabilizer composition should be mixed amongst the pulp to be bleached to ensure that the pulp or pulp slurry or water containing the pulp is stabilized. The contact time should be a few seconds to minutes or hours. As a more specific example, the contact time should be at least 10 minutes, at least 20 minutes, at least 30 minutes or more prior to adding any bleaching agent, like a peroxide. During the contact time, it is preferred that that the pulp and stabilizer composition is agitated or mixed.

Any kind of suitable bleaching agent can be used after addition of the stabilizer composition and/or individual ingredients thereof. For example, at least one peroxide compound and/or at least one peroxide forming compound can be used. Inorganic peroxides and/or organic peroxides can be employed. Hydrogen peroxide and/or a compound containing a peroxyl group and yields hydrogen peroxide can be used. One or more peroxide salts can be used such as sodium peroxide, barium peroxide, lithium peroxide, calcium peroxide, zinc peroxide, magnesium peroxide, or a combination thereof. Examples of organic peroxides include dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide, cyclobutane malonyl peroxide, 2,4-pentanedione peroxide, 2-butanone peroxide, or a combination thereof.

The method of the present invention can be practiced on conventional papermaking machines with modifications that can be easily made in view of the present invention. The method of the present invention can be practiced, for example, on a wet end assembly of a conventional papermaking machine with modifications that can be easily made in view of the present invention. The method can employ many different types of papermaking pulp or combinations thereof. The pulp or stock can be treated with the stabilizer composition, or individual ingredients thereof, at any location in the papermaking system before bleaching and formation of the paperweb on the wire, e.g., an addition point prior to the headbox in the system. The separate additions of these components to the pulp according to other indicated options also can be done at any of these locations in the papermaking system.

The methods of the present invention can be practiced on any pulp related applications, including, for example, where pulps are treated and dewatered. The methods can be practiced, for example, on conventional paper making machines (such as a Fourdrinier type paper machine), for example, on wet end assemblies of paper making machines, with modifications that can be made in view of the present invention. On the wet end, a paper machine can include, for example, a pulp tank, a blend chest, a stuff box, a white water silo, a fan pump, a screen, and a head box. The paper machine can optionally include one or more refiners. The individual stabilizing agents, and optional sulfur-containing compound, can be added to the pulp at or between any of these machine components. The individual stabilizing agents, and optional sulfur-containing compound, can be added to the pulp at a suitable point that allows sufficient time for protection of the bleaching agent during bleaching of the pulp fiber.

The stabilizer composition, and optional sulfur-containing compound, can be added to the pulp in an amount, for example, of from about 0.01% by weight to about 10% by weight based on the dry weight of the pulp, or from about 0.05% by weight to about 5.0% by weight, or from about 0.1 by weight to about 2.5% by weight, or from about 0.2 by weight to about 1.5% by weight based on the dry weight of the pulp, though other amounts can be used. These addition amounts relative to the pulp can apply to any manner in which the composition is introduced into the pulp slurry.

The amount of the stabilizer composition used can vary depending on the specific components present and sulfur-containing compound used, and generally can be added to the pulp in an amount, for example, at least about 0.1 pound polymer per ton paperstock, based on dried solids of the pulp, or in an amount from about 0.5 pound to about 8.0 pounds per ton of paperstock, or from about 1.0 pound to about 6.0 pounds per ton of paperstock, or from about 1.5 pounds to about 4.0 pounds per ton of paperstock, or from about 2.0 pounds to about 3.0 pounds polymer per ton of paperstock, based on the dried solids of the pulp, though other amounts can be used.

The stabilizer composition (formulation) can be formulated by sequentially or simultaneously combining the components in a fluid medium, such as water. The order of addition of the components is not limited. The various ingredients that form the stabilizer compositions of the present invention can be mixed together using conventional mixing techniques, such as a mixer, blender, stirrer, and/or an open vessel. Before and/or following aqueous dispersion of the individual stabilizing agents, and optional sulfur-containing compound, the pH of the resulting combination generally can be controlled, for example, to a defined level of a pH of from about 2 to about 14, or a pH of from about 4 to about 12, or a pH of from about 7 to about 11, or from about 9 to about 10. These pH ranges can apply to the composition and/or to the composition in an aqueous solution. Adjustment of the pH of the composition can be accomplished, for example, through the addition of either sodium hydroxide or ammonium hydroxide (aqueous ammonia). The stabilizer composition can include one or more additives, such as dyes, pigments, defoamers, biocides, pH adjusting agents, and/or cationic starch, and/or other conventional paper making or processing additives.

The stabilizer composition can be prepared as masterbatches for dilution at a later time or the desirable concentration can be made at the same time that the composition is prepared. The stabilizer composition can be prepared on-site or off-site or parts or components of the composition can be prepared or pre-mixed off-site or on-site prior to the ultimate formation of the composition. The stabilizer compositions can be formed immediately prior to their introduction into the papermaking process or sheet making process, or the compositions can be prepared beforehand, such as before use, minutes before use, hours before use, or days or weeks or months before use, for example, within about 2 to 3 weeks of usage. When the stabilizer compositions is introduced as a pre-mixture, the pre-mixture can be made from about 1.0 to about 100 seconds before their introduction into the papermaking process, or from about 1.0 hour to about 5 hours, from about 1.0 hour to about 10 hours, from about 1.0 hour to about 24 hours before use, from about 1.0 day to about 7.0 days, from about 1.0 day to about 30 days, from about 1.0 day to about 60 days, or from about 1 day to about 180 days, before use.

The individual stabilizing agents, and optional sulfur-containing compound, as part of a single pre-mixed composition or as separate components, can be added to many different types of papermaking pulp, stock, or combinations of pulps or stocks. For example, the pulp can contain virgin pulp and/or recycled pulp, such as virgin sulfite pulp, broke pulp, Kraft pulp, soda pulp, thermomechanical pulp (TMP), alkaline peroxide mechanical pulp (APMP), chemithermomechanical pulp (CTMP), chemimechanical pulp (CMP), groundwood pulp (GP), mixtures of such pulps, and the like. The Kraft pulp can be, for example, a hardwood kraft pulp, a softwood haft pulp, or combinations thereof. The recycled pulp can be or include waste paper, old corrugated containers (OCC), and other used paper products and materials. For example, there are a variety of mechanical pulping methods to which this invention can be applied. Thermomechanical pulp (TMP) uses a combination of heated wood chips and mechanical processes. Stone Groundwood (SGW) grinds or macerates the wood chips. Chemithermomechanical pulp (CTMP) uses a variety of chemicals, heat, and grinding techniques to produce pulp. Different types of pulp involve different types of paper although many papers can use a combination or “blend” of several different types of pulp and recycled/recovered paper. The papermaking pulp or stock can contain cellulose fibers in an aqueous medium at a concentration, for example, of at least about 50% by weight of the total dried solids content in the pulp or stock, though other concentrations may be used. These pulp formulations can be referred to as fiber furnishes.

The pulps or stocks of the present invention can be treated with one or more optional additives within the papermaking system. These additives can be added before, during, and/or after introduction of the stabilizer composition or individual stabilizing agents, and optional sulfur-containing compound, These optional additives can include, for example, additional polymers such as cationic, anionic and/or non-ionic polymers, clays, other fillers, dyes, pigments, defoamers, pH adjusting agents such as alum, sodium aluminate, and/or inorganic acids, such as sulfuric acid, microbiocides, supplemental water retention aids such as cationic colloidal alumina microparticles, coagulants, supplemental flocculants, leveling agents, lubricants, defoamers, wetting agents, optical brighteners, pigment-dispersing agents, cross-linkers, viscosity modifiers or thickeners, or any combinations thereof, and/or other conventional and non-conventional papermaking or processing additives. Temperature and pH can be varied based on the particular stabilizing agents, and optional sulfur-containing compound, used.

The stabilizer compositions of the present invention can be used for uses other than, or in addition to, stabilization of peroxides during the bleaching of pulp. The stabilizer compositions can be used as chelants in other contexts where there is a desire to sequester metal and other ions. The stabilizer compositions can also be used as alkaline cleaning-in-place (CIP) agents, scale inhibitors, felt cleaners, viscosity reduction agents, corrosion inhibitors, and anti-freeze agents. Other uses of the stabilizer compositions that can be appreciated by one of ordinary skill in the art are also included within the present invention.

The present invention includes the following aspects/embodiments/features in any order and/or in any combination:

1. A stabilizer composition comprising:

a) about 50 wt % to about 80 wt % of at least one aminocarboxylate;

b) about 5.0 wt % to about 20 wt % of at least one hydroxy acid;

c) about 1.0 wt % to about 10 wt % of at least one polyamino acid, at least one iminodisuccinate, or both,

wherein a), b), and c) are different from each other, and wherein each wt % is based on the total weight of the stabilizer composition.

2. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising water. 3. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising less than 0.05 wt % magnesium based on the total weight of the stabilizer composition. 4. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising less than 0.0001 wt % magnesium based on the total weight of the stabilizer composition. 5. The stabilizer composition of any preceding or following embodiment/feature/aspect, wherein the stabilizer composition is free of magnesium. 6. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising less than 0.05 wt % phosphate based on the total weight of the stabilizer composition. 7. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising less than 0.0001 wt % phosphate based on the total weight of the stabilizer composition. 8. The stabilizer composition of any preceding or following embodiment/feature/aspect, wherein the stabilizer composition is free of phosphate. 9. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising less than 0.05 wt % silicate based on the total weight of the stabilizer composition. 10. The stabilizer composition of any preceding or following embodiment/feature/aspect, further comprising less than 0.0001 wt % silicate based on the total weight of the stabilizer composition. 11. The stabilizer composition of any preceding or following embodiment/feature/aspect, wherein the stabilizer composition is free of silicate. 12. The stabilizer composition of any preceding or following embodiment/feature/aspect, comprising at least one aminocarboxylate and at least one polyamino acid. 13. The stabilizer composition of any preceding or following embodiment/feature/aspect, comprising at least two aminocarboxylates. 14. The stabilizer composition of any preceding or following embodiment/feature/aspect, comprising at least one aminocarboxylate, at least one polyamino acid, and at least one hydroxy acid. 15. A method of stabilizing the bleaching of pulp at an alkaline pH comprising:

adding from about 1.0 lb. to about 5.0 lbs. per dry ton of pulp of the stabilizer composition of any preceding or following embodiment/feature/aspect to a pulp composition prior to any bleaching of said pulp composition; and

adding at least one peroxide to the pulp composition at an alkaline pH after addition of the stabilizer composition to form a bleached pulp.

16. The method of any preceding or following embodiment/feature/aspect, further comprising adjusting the pH of the pulp composition to a pH of from about 9 to about 12. 17. The method of any preceding or following embodiment/feature/aspect, further comprising heating the pulp composition to a temperature of from about 120° F. to about 160° F. 18. The method of any preceding or following embodiment/feature/aspect, further comprising adding at least one sulfur-containing compound to the pulp composition prior to the addition of the at least one peroxide. 19. The method of any preceding or following embodiment/feature/aspect, wherein the at least one sulfur-containing compound comprises at least one sulfite. 20. The method of any preceding or following embodiment/feature/aspect, further comprising forming the bleached pulp into a paper product having a brightness greater that that achieved by using a single stabilizing agent.

The present invention can include any combination of these various aspects, features, or embodiments above and/or below as set forth in sentences and/or paragraphs. Any combination of disclosed features herein is considered part of the present invention and no limitation is intended with respect to combinable features.

The present invention will be further clarified by the following examples, which are intended to be purely exemplary of the present invention, in which parts and percentages are proportions by weight unless otherwise specified.

EXAMPLES

In Examples 1 and 2, the aminocarboxylate was DPTA, the polyamino acid was polyaspartic acid, and the hydroxy acid was citric acid.

Example 1

This example demonstrates the surprising and unexpected results achieved by the compositions and methods of the present invention. Pulp was obtained from a standard paper mill operating at alkaline conditions and processing softwood, such as Douglass fir and spruce furnishes. The Control was no formulation in the pulp at all. Two comparative formulations and two test formulations were prepared. Comparative formulation 1 contained amino phosphonic acid with a phosphate concentration of 38.4 mg/L, and comparative formulation 2 was a blend of amino phosphonic acid, aminocarboxylate, and a hydroxy acid with a phosphate concentration of 4.5 mg/L. Test formulation 1 contained 65.00 wt % aminocarboxylate, 5.00 wt % polyamino acid, 15.00 wt % water, and 15.00 wt % of a citric acid solution (50 wt % citric acid based on the total weight of the citric acid solution) based on the total weight of test formulation 1. Test formulation 2 contained 65.00 wt. % aminocarboxylate, 15.00 wt % water, 15.00 wt % of the citric acid solution, and 5.00% iminodisuccinate based on the total weight of the test formulation 2. Neither test formulation had any appreciable phosphate concentration. One of the goals of this experiment was to try to achieve suitable chelation and peroxide stabilization without the use of phosphate. Different amounts of the formulations were tested per ton of pulp (dry weight). The formulations were added prior to addition of peroxide to the pulp. The resulting bleached pulps were formed into oven dried hand sheets. Brightness and elemental tests were then performed on hand test sheets to probe the effectiveness of the test formulation of achieving suitable chelation and peroxide stabilization relative to the comparative formulations.

Brightness of the resulting paper product is an accepted measure of how well bleaching occurred, which in turn is controlled by how well the bleaching agent, for example, hydrogen peroxide, was stabilized during treatment of the pulp. The hand sheets produced were tested using the TAPPI Brightness Test Method T 452 om-08. 45° illumination and 0° viewing geometry with the illuminating and viewing beams were adjusted so that the hand sheets were evaluated on an arbitrary but specific scale to measure the directional reflectance factor at 457 nm. The results are shown in Table 1. Overall, these results were both surprising and unexpected because on average the phosphate-free test formulations achieved brightness scores that was comparable or exceeded those of the comparative phosphate formulations. In essence, the examples show that non-phosphate, magnesium-free and silicate-free formulations can achieve similar, the same, or better brightness results as phosphate-containing formulations. The test formulations are representative of the stabilizer compositions of the present invention and demonstrate that they can produce acceptable brightness in paper products without the use of environmentally damaging phosphates.

TABLE 1 Sheet Sheet Sheet Sheet Formulation 1 2 3 4 Average Gain % Gain Brightness Values Control 49.1 48.1 48.8 48.7 48.7 — — Comparative 48.8 48.3 48.5 48.5 48.5 −0.3% −0.1 Formulation 1 1 lb/ton Test 48.2 48.6 49 48.3 48.5 −0.3% −0.1 Formulation 1 2 lb/ton Test 48.6 48.7 48.8 48.9 48.8 0.2% 0.1 Formulation 1 1 lb/ton Test 49.9 49.3 49.4 49.3 49.48 1.6% 0.8 Formulation 2 2 lb/ton Test 49.4 49.6 49.6 49.5 49.5 1.7% 0.9 Formulation 2 1 lb/ton Comparative 50.4 49.6 49.7 49.3 49.8 2.2% 1.1 Formulation 2 2 lb/ton Test 51 51.1 50.9 50.5 50.9 4.5% 2.2 Formulation 1 4 lb/ton Test 51.8 51.7 51.9 51.7 51.8 6.4% 3.1 Formulation 2 4 lb/ton

After the brightness testing, the hand sheets were then ashed in preparation for elemental analysis to determine the amount of metals that were present in the sheets. The lower the metal levels, the better the formulations performed in chelating the metal ions that can degrade peroxide and thus interfere with the bleaching of the pulp. The elemental analysis was carried out using inductively coupled plasma spectroscopy. The results of this analysis are shown in Table 2 and for convenience some of the earlier described brightness results are also provided. The phosphate-free test formulations were able to achieve metal levels comparable or even lower than the phosphate-containing comparative formulations. Manganese and iron are recognized as more troublesome transition metals with respect to peroxide bleaching efficiency. The Mn/Fe ratio is a particularly revealing measure of how well a stabilizer formulation was able to chelate metal ions during bleaching. Significantly, the test formulations were both able to achieve Mn/Fe ratios below 1.0.

TABLE 2 Comparative Comparative Test Test Test Test Formulation 1 Formulation 2 Formulation 1 Formulation 2 Formulation 1 Formulation 2 Control 1 lb/ton 2 lb/ton 2 lb/ton 2 lb/ton 4 lb/ton 4 lb/ton Brightness 48.70 48.53 49.80 48.30 49.48 50.88 51.78 Fe (ppm) 13.30 10.60 9.80 8.80 8.60 11.00 10.10 Mn (ppm) 25.40 20.80 14.30 17.00 15.30 7.80 7.40 Cu (ppm) 19.50 19.50 10.80 15.40 8.60 4.00 8.30 Mn/Fe 1.91 1.96 1.46 1.93 1.78 0.71 0.73 ratio

From these results, it can be appreciated that the formulations of the present invention were able to replace conventional phosphates and achieve comparable results for brightness in paper and mitigate the effects of metals that negatively impact bleaching.

Example 2

This example further demonstrates the surprising and unexpected results achieved by the compositions and methods of the present invention. Pulp was obtained from a standard paper mill operating at alkaline conditions and processing softwood, such as Douglass fir and spruce furnishes. The Control was no formulation in the pulp at all. Three comparative formulations and one test formulation was prepared. Comparative formulation 1 contained 65.00 wt. % aminocarboxylate, 30.00 wt % water, and 5.00 wt % iminodisuccinate based on the total weight of the formulation. Comparative formulation 2 contained 80.00 wt % water, 15.00 wt % of the citric acid solution (50 wt % citric acid based on the total weight of the citric acid solution), and 5.00% iminodisuccinate based on the total weight of the formulation. Comparative formulation 3 contained 90.00 wt % water, 5.00 wt % iminodisuccinate, and 5.00 wt % polyamino acid based on the total weight of the test formulation. Test formulation 1 contained 65.00 wt. % aminocarboxylate, 15.00 wt % water, 15.00 wt % of the citric acid solution, and 5.00% iminodisuccinate based on the total weight of the formulation. 1 pound of the test or comparative formulations was tested per ton of pulp (dry weight). Except where noted, the procedures of Example 1 were followed in this example, and the formulations were added prior to addition of peroxide to the pulp. The resulting bleached pulps were formed into oven dried hand sheets. Brightness and elemental tests were then performed on hand test sheets to probe the effectiveness of the formulation of achieving suitable chelation and peroxide stabilization relative to the comparative formulations.

Some of the results are shown in Table 3 below. Overall, these results were both surprising and unexpected. As can be seen in the results below, the formulation of the present invention increased the brightness significantly (over 3 points) whereas the other comparative formulations that contained some of the components of the inventive formulation, but not all of the components, did not perform as well. These results show the effectiveness of the formulations of the present invention and the interaction of each component. The test formulation is representative of the stabilizer compositions of the present invention and demonstrate that they can produce acceptable brightness in paper products without the use of environmentally damaging phosphates.

TABLE 3 Sheet Sheet Sheet Sheet Formulation 1 2 3 4 Average Diff % Brightness Values Control 66.4 66.6 66.6 66.5 66.525  0% Test 69.9 69.9 69.7 69.6 69.775 3.25%  Formulation 1 1 lb/ton Comparative 67.1 67.3 67 67.1 67.125 0.6% Formulation 1 1 lb/ton Comparative 68.8 68.8 68.7 68.7 68.75 2.225%  Formulation 2 1 lb/ton Comparative 68.1 68.2 68.5 68.1 68.225 1.7% Formulation 3 1 lb/ton

After the brightness testing, the hand sheets were then ashed in preparation for elemental analysis to determine the amount of metals that were present in the sheets. The lower the metal levels, the better the formulations performed in chelating the metal ions that can degrade peroxide and thus interfere with the bleaching of the pulp. The elemental analysis was carried out using inductively coupled plasma spectroscopy. The results of this analysis are shown in Table 4.

From these results, it can be appreciated that the formulation of the present invention was capable of providing significantly higher brightness levels and was able to able to mitigate the effects of metals that negatively impact bleaching.

TABLE 4 Comparative Comparative Comparative Test Formulation Formulation Formulation Formu- 1 2 3 lation 1 Control 1 lb/ton 1 lb/ton 1 lb/ton 1 lb/ton Brightness 66.525 67.125 68.75 68.225 69.775 Fe (ppm) 88.6 25.4 26.1 22.1 30.5 Mn (ppm) 11.4 8.3 14.6 10.8 7.2 Cu (ppm) 5.0 4.0 4.1 3.8 5.3

Applicants specifically incorporate the entire contents of all cited references in this disclosure. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present invention without departing from the spirit or scope of the present invention. Thus, it is intended that the present invention covers other modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

What is claimed is:
 1. A stabilizer composition comprising: a) about 50 wt % to about 80 wt % of at least one aminocarboxylate; b) about 5.0 wt % to about 20 wt % of at least one hydroxy acid; c) about 1.0 wt % to about 10 wt % of at least one polyamino acid, at least one iminodisuccinate, or both, wherein a), b), and c) are different from each other, and wherein each wt % is based on the total weight of the stabilizer composition.
 2. The stabilizer composition of claim 1, further comprising water.
 3. The stabilizer composition of claim 1, further comprising less than 0.05 wt % magnesium based on the total weight of the stabilizer composition.
 4. The stabilizer composition of claim 3, further comprising less than 0.0001 wt % magnesium based on the total weight of the stabilizer composition.
 5. The stabilizer composition of claim 4, wherein the stabilizer composition is free of magnesium.
 6. The stabilizer composition of claim 1, further comprising less than 0.05 wt % phosphate based on the total weight of the stabilizer composition.
 7. The stabilizer composition of claim 6, further comprising less than 0.0001 wt % phosphate based on the total weight of the stabilizer composition.
 8. The stabilizer composition of claim 7, wherein the stabilizer composition is free of phosphate.
 9. The stabilizer composition of claim 1, further comprising less than 0.05 wt % silicate based on the total weight of the stabilizer composition.
 10. The stabilizer composition of claim 9, further comprising less than 0.0001 wt % silicate based on the total weight of the stabilizer composition.
 11. The stabilizer composition of claim 10, wherein the stabilizer composition is free of silicate.
 12. The stabilizer composition of claim 1, comprising at least one aminocarboxylate and at least one polyamino acid.
 13. The stabilizer composition of claim 1, comprising at least two aminocarboxylates.
 14. The stabilizer composition of claim 1, comprising at least one aminocarboxylate, at least one polyamino acid, and at least one hydroxy acid.
 15. A method of stabilizing the bleaching of pulp at an alkaline pH comprising: adding from about 1.0 lb. to about 5.0 lbs. per dry ton of pulp of the stabilizer composition of to a pulp composition prior to any bleaching of said pulp composition; and adding at least one peroxide to the pulp composition at an alkaline pH after addition of the stabilizer composition to form a bleached pulp, wherein said stabilizer composition comprises: a) about 50 wt % to about 80 wt % of at least one aminocarboxylate; b) about 5.0 wt % to about 20 wt % of at least one hydroxy acid; c) about 1.0 wt % to about 10 wt % of at least one polyamino acid, at least one iminodisuccinate, or both, wherein a), b), and c) are different from each other, and wherein each wt % is based on the total weight of the stabilizer composition.
 16. The method of claim 15, further comprising adjusting the pH of the pulp composition to a pH of from about 9 to about
 12. 17. The method of claim 15, further comprising heating the pulp composition to a temperature of from about 120° F. to about 160° F.
 18. The method of claim 15, further comprising adding at least one sulfur-containing compound to the pulp composition prior to the addition of the at least one peroxide.
 19. The method of claim 18, wherein the at least one sulfur-containing compound comprises at least one sulfite.
 20. The method of claim 15, further comprising forming the bleached pulp into a paper product having a brightness greater that that achieved by using a single stabilizing agent.
 21. The stabilizer composition of claim 1, wherein c) is at least one iminodisuccinate.
 22. The stabilizer composition of claim 1, wherein c) is at least one iminodisuccinate and at least one polyamino acid.
 22. The method of claim 15, wherein c) is at least one iminodisuccinate.
 23. The method of claim 15, wherein c) is at least one iminodisuccinate and at least one polyamino acid. 